Push or Pull GMAW

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I posted a reply recently stating a push (forehand) torch movement gives more penetration with GMAW than pull (backhand) torch movement. I recently looked it up and found as others suggested within this forum that in fact pushing a GMAW offers less penetration. I never had to prove or test the outcome of such theory but I would like to discuss why I came to the conclusion that push obtained more penetration than pull with GMAW.Years ago working for a stainless steel fabrication co. building a mammoth furnace heat shield out of 12 gauge 316 stainless steel, we had an applications engineer rep come in from the engineering/design company telling us how to weld the 12 gauge. He had us use 316LT .035” wire with 75/25 shielding.We had to run vertical down butt weld seams in order to avoid/control distortion. He told us that if we pushed the weld we would be in trouble with heat warp. (what would you think, he’s the engineer?).We did the vertical down with machine set hot and fast, way hotter that if I was to push the same weld. That is why I was under the impression that push had more penetration.Also 316 LT is cored wire. I usually run stainless with Solid LSI wire and Tri Mix Shielding, so I am not sure if that would make a difference or not. I’m thinking not.Anyhow, I know this subject has been beat to death but I wanted to clear up my posting principles of right and wrong. Thanks.
Reply:My "Old" welding manual states that either may be used, it seems to indicate there is little difference.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:Push preheats the joint and lays the bead more on top.Pull drives the arc into the joint and lays the bead deeper and narrower.The top profile of the beads will show the same thing.  Push makes for a wider flatter bead and pull  makes for a taller narrower bead.I am not talking sheet metal because you can get all the penetration you want with sheet just by using more heat.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:like david said. pulling the wire causes the wire to drive itself deeper into the hot weld pool and plate which gives more penetration. Pulling causes the wire to push on to cold plate and drive the penetration down slightly. For example i might be burning in some 1/4 really hot with a pull technique but then i get some 3/16 i need to weld. Instead of resetting the machine i just switch to a push technique and don't burn through because i'm getting slightly less penetration. --Gol'
Reply:Well,I went back and took a look again at the 'ole manual.  There at the bottom of page 94 it states" The pulling or drag technique is usually best for light gage metals and the pushing technique for heavy materials." from Welding Technology 2nd ed, American Technical Publishers, Giachino/Weeks/Johnson.  I guess I forgot to turn the page.Since this is a widely accepted manual from a few years ago,  I don't think that it would be wrong.  Which I guess if you drag, you make less heat, which in my way of thinking, you get actually less penetration, because you are pushing the wire into a cold weld.  If you push, you make more heat and the wire pushes "down" into the soft molten puddle.  This is also the way I was taught, but I guess I could be wrong, but the welds that I have examined both ways while the pushing may be more spread out, it is because of the heat affected area and a larger area is fused with deep penetration.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:that book is incorrect pulling provides deeper penetration. --Gol'
Reply:Originally Posted by Go1lumthat book is incorrect pulling provides deeper penetration.
Reply:Originally Posted by OMSI posted a reply recently stating a push (forehand) torch movement gives more penetration with GMAW than pull (backhand) torch movement. I recently looked it up and found as others suggested within this forum that in fact pushing a GMAW offers less penetration. I never had to prove or test the outcome of such theory but I would like to discuss why I came to the conclusion that push obtained more penetration than pull with GMAW.Years ago working for a stainless steel fabrication co. building a mammoth furnace heat shield out of 12 gauge 316 stainless steel, we had an applications engineer rep come in from the engineering/design company telling us how to weld the 12 gauge. He had us use 316LT .035” wire with 75/25 shielding.We had to run vertical down butt weld seams in order to avoid/control distortion. He told us that if we pushed the weld we would be in trouble with heat warp. (what would you think, he’s the engineer?).We did the vertical down with machine set hot and fast, way hotter that if I was to push the same weld. That is why I was under the impression that push had more penetration.Also 316 LT is cored wire. I usually run stainless with Solid LSI wire and Tri Mix Shielding, so I am not sure if that would make a difference or not. I’m thinking not.Anyhow, I know this subject has been beat to death but I wanted to clear up my posting principles of right and wrong. Thanks.
Reply:I can’t even imagine pushing a vertical down weld. That would mean angle the torch downwards and then run downhill. We ran the weld pulling downhill hot and fast and I mean fast. That may be why the heat affected zone (HAZ) did not have the heat input/saturation to warp so much. Stainless steel does not conduct heat as well as mild steel, so there are some variables to consider as far as heat input when welding stainless let alone 12 gauge sheet steel.All in all, the job went fine. I actually did push some of the welds and even though the puddle was wider and flatter the material did not warp any more that the pull technique as far as I could tell but then again (I am not an engineer: D ).With the proper joint preparation a push technique seems to provide 100% penetration as far as I am concerned. I just never took the time or found the need to scrutinize the difference between the two methods.Thanks. :cool
Reply:Pulling was the normal way I did GMAW with my MM175, with .023", .030", and .035".  Then I got a feeder for my PowCon 300SM.  With .045" solid wire and argon mix gas, this machine's particular settings got MUCH better overall results when pushing the bead, even on a vertical down.  Don't ask me to explain.  All my machines since have worked just fine with pulling the bead.There, that settled nothing!
Reply:I use both.  Depends on the material being welded, thickness, etc.
Reply:I may be wrong in this, but I was taught pushing preheats the metal in front of you and allows the bead greater penetration.  Dragging/pulling offers little to no preheat thus less penetration, and better for thinner metals.    That being said, I think gun angle has a great percentage to how this matters.   90º would it be pushing or pulling? LOL..
Reply:Look here in the mig welding guide.http://www.millerwelds.com/resources...g-your-skills/Here it is  Pictures and all.http://www.millerwelds.com/resources...tips/MIG_tips/ Quote from Miller website**************************************************  ****************************** A drag or pull gun technique will give you a bit more penetration and a narrower bead. A push gun technique will give you a bit less penetration, and a wider bead. (Refer to Diagram 3. Effect of Electrode Position and Welding Technique)**************************************************  ******************************David Last edited by David R; 11-14-2008 at 06:35 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:If you are using a cored wire like you said (you didn't say if it was metal cored or flux cored), pushing a flux cored wire will lead to slag entrapment.  I proved that point here:http://weldingweb.com/vbb/showthread.php?t=24000as far as pushing vert down, I wouldn't do that.